Methods were developed for quantitating cell spreading and migration using the facilities at the National Center for Microscopy and Imaging Research. These methods were used for studying the effects of ions on the mechanisms of action of integrin adhesion receptors. Rat basophilic leukiemia (RBL) cells were plated on fibronectin and adhered via integrins. Cells spread within 60 min. However, in medium lacking potassium, RBL cells failed to spread, although they maintained itegrindependent adherence. Spreading was restored by adding a physiological concentration of potassium. Other cell types tested, including carcinomas, melanomas and neutrophils, also required potassium for spreading. These data implicate potassium ion channels in integrin-dependent pathways controlling the progression of cell adhesion to cell spreading. In order to quantify the effect, the area measurements were performed on cells in potassium free medium vs. normal medium. Low power transmitted light images of cells were digitized using a Photometrics cooled CCD camera and Mirage software, developed by Dr. Gary Fan at the NCMIR. The images were then thresholded and binarized using NIH Image which was also used to obtain area measurements. The manuscript detailing this work has been submitted.